1. Field
The following description relates to an optical transport network (OTN), and more particularly, to a technology for protection switching in the OTN.
2. Description of the Related Art
An optical transport network supports a wide bandwidth, high reliability, well-developed protection switching function, and operations administration and management (OAM) technologies. Accordingly, research on transmission of packet data, which shows a remarkable growth, through an optical transport network has been actively conducted, and the relevant standardization is in progress under the auspices of the International Telecommunication Union Telecommunication standardization sector (ITU-T). In particular, ITU-T SG 15 has standardized a flexible optical channel data unit (hereinafter, referred to as “ODUflex) that can receive Ethernet data more efficiently through an OTN, as well as has developed a hitless adjustment of ODUflex(GFP) (HAO) protocol and released G.7044 standard for HAO, which allows for increase or decrease of a size of an ODUflex(GFP) signal (i.e., bandwidth resizing operation) without affecting a service that is being operated in the network. In an OTN that is operated in (1+1) form, when an ODUflex signal on a working path is increased or decreased, the ODUflex signal on a corresponding protection path should also be increased or decreased simultaneously. In the actual network, however, the working path and the protection path are configured differently, and thus the working path and the protection path have different latencies from each other. According to the present ITU-T G.7044 standard, in the process of executing a HAO protocol, a bandwidth of an ODUflex signal is increased or decreased immediately upon a value of a network connectivity status (hereinafter, referred to as “NCS”) signal being set to ACK in response to a tributary slot connectivity check (hereinafter, referred to as “TSCC”) signal, without the consideration of the latencies of a working path and a protection path. Therefore, the use of a HAO protocol defined in the current G.7044 standard may cause data loss due to a difference in latency between the working path and the protection path, at the time of increasing or decreasing the bandwidth of an ODUflex signal.
In Korean Patent Publication No. 10-2014-0031648, protection switching in an optical transport network is disclosed, which only determines a communication failure of an individual optical line terminal (OLT) and does not take into account timing delays.